This invention relates generally to chemical vapor deposition processes, and compositions useful therein, that may be used in semiconductor and other manufacturing technologies.
Films containing two or more metals are generally known in the art, and may be referred to as multi-metallic films. A multi-metallic film may be formed from an alloy of two or more metals, and/or from one or more metal compounds, where a metal compound itself may contain more than one metal. Typical metal compounds are metal borides, nitrides, oxides and sulfides. Multi-metallic films find use in the semiconductor industry, and have been proposed for various special applications. For example, a Ti1xe2x88x92xAlxN2 thin film has been proposed as a useful barrier layer which may be placed between a silicon substrate and an overlying metallization layer. While Ti1xe2x88x92xAlxN2 films may be prepared by sputtering, that is a complicated process and is not well controlled in terms of metal stoichiometry, especially for via filling.
A thin film of a multi-metallic compound, such a Ti1xe2x88x92xAlxN2, may be formed by flash vaporization of suitable precursor compounds, followed by deposition of the vapor according to a technique known as metalorganic chemical vapor deposition (MOCVD). In a typical MOCVD process, a heat decomposable metalorganic compound, which is commonly referred to as a xe2x80x9cprecursorxe2x80x9d or xe2x80x9csource reagent,xe2x80x9d is contacted with a substrate which has been heated to a temperature above the decomposition temperature of the precursor. Upon contact with the heated substrate, the precursor decomposes to form metallic species, which are then deposited onto a surface so as to form a metallic film or layer. This heat-induced decomposition process may be referred to as pyrolysis. In one version of the MOCVD process, the pyrolysis of the precursor occurs in the presence of a reactant gas so that a metallic compound is formed and then deposited onto a surface. By using more than one precursor, deposition of multi-metallic alloys and compounds is possible.
The semiconductor manufacturing industry has extensive expertise in the use of MOCVD, and employs this process in many production settings. MOCVD is a particularly advantageous process because it allows for strict control of the thickness of the formed layer, and also because a wide variety of substrate geometries may be coated. One example of a prior art apparatus for performing MOCVD is discussed in U.S. Pat. No. 5,399,379 entitled xe2x80x9cLow-Pressure Chemical Deposition Process for Depositing High-Density, Highly-Conformal Titanium Nitride Films of Low Bulk Resistivity.xe2x80x9d
For many semiconductor manufacturing applications, obtaining and maintaining strict control over the stoichiometry of the deposited metallic or multi-metallic layer is paramount. That is, it is usually very important to deposit a metallic or multi-metallic layer such that the molar (or atomic) ratio of the different metals and/or other elements in the layer corresponds very closely to a predetermined value, or falls within a narrow specified range. The stoichiometry (ie., numerical ratio of different metals and/or elements to one another) of the deposited layer can be strictly controlled if the precursors are delivered into the deposition chamber in a highly uniform and regulated manner. In other words, it is highly desirable to control the relative amounts of vaporized precursor molecules which are present in the deposition chamber of the MOCVD apparatus. The precursor delivery system is therefore an important component of the MOCVD process.
In one prior art precursor delivery system, one or more bubblers are used to deliver one or more precursors, in vapor form, into the deposition chamber. The bubblers are used in conjunction with a carrier gas stream which serves to dilute and deliver precursors into the deposition chamber. With the use of conventional bubblers, however, the gas phase ratio of different precursors in the deposition chamber tends to vary, especially when the number of precursors (and hence bubblers) is increased. As a result, conventional bubblers are not very effective at providing strict control over the composition of a vapor, and hence the composition of the deposited layer.
Flash vaporization has been described as one approach to achieving a controlled delivery of a precursor into a deposition chamber. See, e.g., U.S. Pat. No. 5,204,314, entitled xe2x80x9cMethod for Delivering an Involatile Reagent in Vapor Form to a CVD Reactor,xe2x80x9d and U.S. Pat. No. 5,536,323, entitled xe2x80x9cApparatus for Flash Vaporization Delivery of Reagents.xe2x80x9d As described in these patents, the delivery of a precursor vapor into the deposition chamber of a CVD apparatus may be accomplished by providing the precursor in a liquid form, either neat or in solution, and flowing the liquid onto a flash vaporization matrix structure which has been preheated to a temperature sufficient to flash vaporize the precursor source material. A carrier gas may optionally be flowed past the flash vaporization matrix structure to form a vapor mixture containing the carrier gas and the flash vaporized precursor or decomposition product(s) thereof. These precursor delivery systems, as described in the aforementioned patents, have addressed many of the problems associated with controlled delivery of precursors into deposition chambers.
Although MOCVD and flash vaporization are known in the art, these processes have not, to date, been effectively used to produce multi-metallic films having metal stoichiometries within tight specifications. Thus, there exists a need for processes that may be used to prepare multi-metallic films. The present invention addresses this need and provides further related advantages as described herein.
In one aspect, the present invention provides a composition that includes first and second metalloamide compounds. The first metalloamide compound comprises (i.e., has a structure which includes the structural unit) M1(NR1R2) and the second metalloamide compound comprises M2(NR3R4), wherein M1 and M2 are metals such that M1 and M2 are non-identical; N is nitrogen; and each of R1, R2, R3 and R4 is independently selected from hydrogen and organic groups. Here and throughout this disclosure, where the invention provides that at least first and second metalloamide compounds are present in a composition or method, the composition or method may contain or involve additional, e.g., third, metalloamide compounds.
In another aspect, the present invention provides a process for forming a source material, where the source material may be used in, for example, flash vaporization and/or chemical vapor deposition. The inventive process includes the steps of: providing a first metalloamide compound comprising the structural unit M1(NR1R2), where M1 is a metal; N is nitrogen; and each of R1 and R2 is independently selected from hydrogen and organic groups; providing a second metalloamide compound comprising the structural unit M2(NR3R4), wherein M2 is a metal; N is nitrogen; and each of R3 and R4 is independently selected from hydrogen and organic groups; and combining the first and second metalloamide compounds to form the source material.
In another aspect, the present invention provides a process for forming a multi-metallic vapor. The inventive process includes the steps of: providing a liquid multi-metallic mixture which includes first and second metalloamide compounds, where the first metalloamide compound contains a metal that is not present in the second metalloamide compound; and contacting the liquid multi-metallic mixture with a heated surface to vaporize the mixture and form the multi-metallic vapor.
In another aspect, the present invention provides a process for forming a multi-metallic layer on a substrate. The inventive process includes the steps of: providing a multi-metallic mixture that includes first and second metalloamide compounds, where the first metalloamide compound contains a metal that is not present in the second metalloamide compound; vaporizing the multi-metallic mixture by flash or other vaporization technique to form a multi-metallic vapor; and depositing at least a portion of the multi-metallic vapor onto a substrate to form a multi-metallic layer.
In another aspect, the present invention provides that in a chemical vapor deposition process for depositing gas-phase components onto a surface, the gas-phase components are formed by a process that includes vaporization of a multi-metallic mixture, wherein the multi-metallic mixture includes first and second metalloamide compounds, the first metalloamide compound containing a metal that is not present in the second metalloamide compound. The vaporization process is preferably a flash vaporization process.
In another aspect, the present invention provides a process for forming an electronic device. The inventive process includes the steps of: providing a multi-metallic mixture that includes, among other possible components, first and second metalloamide compounds, where the first metalloamide compound contains a metal that is not present in the second metalloamide compound; vaporizing the multi-metallic mixture, preferably by flash vaporization to form a multi-metallic vapor; depositing at least a portion of the multi-metallic vapor onto a substrate to form a multi-metallic layer; and utilizing the substrate having the multi-metallic layer, or a modified version thereof, as a component in an assembly, the assembly defining the electronic device.
These and related aspects of the present invention are described in more detail below.